Conversion of methylcyclopentane to benzene



,1 2,861,944 Patented Nov. 25, 1958 United States Patent Office CONVERSION OF METHYLCYCLOPENTANE TO BENZENE John R. Coley, Gary, Ind., Bernard L. Evering, Chicago, IlL, and John D. McColluni, Hammond, Ind., assignors to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application June 29, 1955, Serial No. 518,764 12 Claims. (Cl. 208--92) This invention relates specifically to conversion of methylcyclopentane to benzene with supported platinum catalyst at low pressure and it pertains more generally to low pressure hydroforming of light naphtha charging stocks containing substantial amounts of methylcyclopentane and to combinations of such loW pressure operations with higher pressure hydroforming operations for maximizing yields'of 95-100 octane number motor fuel and simultaneously producing benzene.

A specific object of the invention is to provide an improved process for converting methylcyclopentane, either in relatively pure state or in admixture with other hydrocarbons such as hexanes, to obtain increased yields of benzene accompanied by isomerization and cyclizing of any C paratfinic hydrocarbons which may be present with a minimum amount of hydrocracking and coke formation. A further object is to accomplish this commercially by means of supported platinum catalyst in a regenerative low pressure hydroforming system in which catalyst activity, selectivity and stability remain high during on-stream operation and can be substantially restored by periodic regeneration and rejuvenation.

Known supported platinum catalyst naphtha hydroforming systems can readily convert most naphthenic naphthas boiling in the range of about 200 to 360 F. into motor fuels of 80 to 90 octane number. Nonregenerative supported platinum hydroforming systems cannot readily convert even this optimum boiling range charge into 95-100 octane number product without cumbersome and expensive solvent extraction and recycling operations. Regenerative supported platinum catalyst hydroforming systems now known can employ wider boiling range charges but they are not effective for converting methylcyclopentane to benzene or for producing benzene inadditionto high quality motor fuel. An object of: this invention is to provide an integrated method and means for maximizing yields of motor fuels having octane numbers of 95 to 100 with simultaneous production of benzene. A further object is to provide an improved integration of low pressure hydroforrning with higher pressure hydroforming. A still further object is to produce benzene from the 140-l80 F. fraction of naphtha with minimum losses to gas and coke formation and maximum isomerization and dehydroaromatization so that hydrocarbons separated from the benzene may be advantageously blended with higher boiling hydroformed naphtha for improving the yield of total 95+ octane number motor fuel. Other objects will be apparent as the detailed description of the invention proceeds.

The invention is based on the discovery that when methylcyclopentane is contacted with a supported plati-- num catalyst at an inlet temperature in the range of about 900 to 950 F., preferably about 930 F., in the presence of about 1 to 10, e. g. 5, mols of hydrogen per mol of charge and at a liquid hourly space velocity in the range of .5 to 8, preferably 2, benzene formation increases rapidly with increasing pressure up to about p. s. i. g. and then declines at higher pressures, hydrocracking of methylcyclopentane reaches a minimum at about 100 p. s. i. g., and the addition of about 50 to 1000, e. g. about 200, parts per million of sulfur has a combined effect of increasing benzene production up to as much as 50 percent while at the same time decreasing carbon formation on the catalyst and catalyst activity decline. The addition of 10 parts per million of chloride to methylcyclopentane under these conditions showed no beneficial effect on benzene formation. It thus appears that the defined amount of sulfur accelerates the isomerization of methylcyclopentane to cyclohexane and simultaneously inhibits coke formation and hydrocracking so that at the low pressure of about 100 p. s. i., i. e. in the range of about 50 to p. s. i., a remarkably effective methylcyclopentane conversion to benzene may be effected and, simultaneously, any C parafiln hydrocarbons present can be isomerized and/or dehydroaromatized.

The invention may be applied to methylcyclopentane per se or to a charge containing substantial amounts thereof when the objective is benzene production. The resulting benzene may thenbe separated and hydrogenated to form cyclohexane by the use of known catalysts and conditions along with hydrogen produced in the methylcyclopentane conversion step.

A preferred charge is a methylcyclopentane fraction of virgin naphtha alone or in combination with the low boiling fraction of a hydroformed product. By hydroforming a naphtha fraction boiling in the range of about 140 to 200 F. or preferably 140 to 180 F. and containing substantial amounts, i. e. 5 to 50 volume percent or more, of methylcyclopentane with a supported platinum catalyst at approximately 100 p. s. i. g. and at a temperature of about 900 to 975 F. in the presence of about 1 to 10 mols of hydrogen per mol of charge and also in the presence of 50 to 1000, e. g. about 200, parts per million of sulfur based on total hydrocarbon charge, remarkably'high yields of benzene are obtained and at the same time the octane number of the other components of thelight naphtha is remarkably enhanced. A particularly advantageous practice is to employ this low pressure sulfur-promoted light naphtha hydroforming operation in conjunction with a hydroforming operation now known to the art, such as Platforming, Cat-forming, Houdriforming or, preferably, Ultraforming. When employed with a regenerative hydroforming system such as Ultraforming, much of the same regeneration equipment may be employed for the low pressure system as is employed in the Ultraforming system. The fraction of ordinary Ultraformed product boiling below 200 F. may be charged with the methylcyclopentane fraction of virgin naphtha to the low pressure system for substantially increasing benzene production and over-all octane number improvement without suffering appreciable yield losses. Hydrogenfrom the Ultraforming portion of the system may supply that required in the low pressure sulfurpromoted hydroforming step. By separating benzene from the stabilized product of the low pressure step and combining the rest of the stabilized product with the high boiling portion of the intermediate or high pressure step, a motor fuel is obtained wherein the light, as well as the heavy, components are of exceptionally high octane number and remarkably hi 'h 100 octane number motor fuel yields are obtainable in addition to the production the accompanying-drawings.- which form a part of the specification .and in which:v

Figure 1 is a graph illustrating the remarkable effect of pressure and the defined amount of added sulfur on the conversionv of methylcyclopentaneito lbenzenea under-.preferred conditions.

Figure. '2 .is a ,graph showing the "effect. of pressureand the defined'amountrof sulfur on hydrocracking :of methylcyclopentane: understhev same. conditions, and

Figure .'3.is a schematicscflow ."diagramsof aplantifor-t; effecting methylcyclopentanei:conversion:in :an integrated hydroforming system;

To demonstrate 'the effect of pressure'andadded sulfur. in the hydroforming .of methylclclopentanea commercial methylcyclopentane .waslpurified by hydrofining. andJ'strip-L.

ping'so that it..contained'less.than parts per million of sulfur and less. than .1 .part perxmillionof chloride-.. The

purified. methylcyclopentaneswas..hydroformed. over -a platinum-alumina catalyst containing; .6 ..weight :percent platinum ata temperature of about 930 F., a space ve-.:

locity of about 2 volumesof methylcyclopentane .per hour.

per volume of catalyst in the presence of 5,000 standard.

cubic feet of once-through hydrogeniper barrel of methylcyclopentane charge'and .underpressures rangingifrom 50'to 400p. s..i. g. Each test employed an on-stream period ofeS hours: Where .sulfur. was-added it was .em-s. ployed'in the form oftertiary butyl .mercaptanz The reactor effluent in each case was analyzed for aromatics content, the catalyst .was analyzed .for icokedeposit and the amount of converted chargeuwhichdidznot.result in;

benzene were considered to be hydrocracked.

The resultszof this experimental program are graphically 1 shown in Figures 1 and 2. Curve 'A. shows that atabout atmospheric pressure only about'20 to percent of the.

methylcyclopentanewas .converted to benzene, thatt'the conversionito benzene increased rapidly as;.pressure was.

increased to about 100 p. s. i. where approximately 45 percent of the charge was converted to benzene .and that with...

further increases in pressure the conversion to .benzenedecreased quite rapidly. Curve'B of Figure'l .shows that methylcyclopentane.charge, the conversion of inethylcyclowhen about 200-pamper million of sulfuris. added to the: 1

pentane to benzene .is markedly increased, .being about percent higher atabout 100 p. s. i. than obtainable in. The effectiveness .of. added sulfur in increasing benzeneproduction is greatest. in .the region'of about 100 p. s. i. and rapidly, diminishes .at

the absence of added sulfur.

higher and lower pressures.

Referring to. Figure 2, Curve .0 shows that in. the .ab-. sence of addedsulfur the hydrocracking of methylcyc1o-.

pentane under the defined conditions reached a minimum in the region of about 100 p. s. i.

had a most remarkable effect of inhibiting.hydrocrackingv at a pressure of about 100 p. s. i. g. althoughit apparently. actually increased hydrocracking at pressures above aboutv 200. p.'s. i. .g.

coke deposit.

this. latter operating pressure resulted in larger yields of total benzene.

parts per million of chloride to methylcvclopentane (instead of the defined amount of sulfur) did not have ap preciable effect on aromatic product and, in fact, at* pressures about 100 p. s. i. and higher the additionof chloride to the charge appeared to be actually detrimentah' While the presence of. added sulfur: had very little elfe'ct Curve D shows .that I the presence of about 200 parts per millionof added sulfur.

Conversion products other. than benzene 1 may be blended with reformed gasolinetozimprove :the yield: and octane number thereof. The. addition :of :10.

on the dehydroaromatization of n-heptane, it was found that aromatics production from normal heptane under the... described conditions likewise reached a maximum in the range of 50 to 150 or about p. s. i. g. Thus a methylcyclopentane fraction of virgin naphtha could be hydroformed under the defined conditions for maximizing aromatics production while minimizing hydrocracking and coke formation.-

While about 200 parts per million is the preferred amount of sulfur to be added to a methylcyclopentane charge'which-is to be hydroformed 'at a pressure of about 100 p. s. i. g., this amount may vary in a range of about 50'to 1000or preferably 100to 500 parts per million, larger amounts in these ranges being used when the charge contains large amounts of paraffins. Amountsof sulfur substantially in excess of 1000 parts per million have a deleterious effect on catalyst life and particularly on the activity and selectivity of the catalyst thereby resulting in-decreased yieldsof desirable products and shorter'onstream-operating periods.- T he sulfur is preferably added in the-form of 'mercaptan sulfur, e. g. astertiary butyl mercaptan, but-it may be added inany other form, such as free. sulfur. H 8, alkyl sulfides'or disulfides, cyclic sulfur" compounds, orother organic sulfur compounds. If 'the' methylcyclopentane fraction of a virgin naphtha stream inherently contains-the desired amount of sulfur, no sulfur' addition from an extraneous source will, of course; be necessary.- The :required' amount of sulfur may be in-' troduccd-with the hydrogen'strea-m; The total sulfur 'in-' troduced into a reactor should not exceed about 1000 parts penmillion basedon total hydrocarbon charging stock" introduced,which-charging stock should contain at" least about 5 percent'and preferably about 50 percent orrnore" of methylcyclopentanev Referring nowto the specific example described incon-' nection with Figure 3, methylcyclopentane"from line '10" is introduced through line 11 to line 12 where it is com mingled with about 5 mols of hydrogen from line 13 per mol of charge and-about-ZOO parts per million of sulfur in" the form of tertiary-butyl'mercaptan introduced through line=14.- The total charge is passed by line 12 through heater 15 and transfer line 16 to lead reactor 17. Eflluent'" from this reactor passes-by lines 18 and 19 through heater 20 and'transfer line 21 to-intermediate reactor 22. Intermediate reactoreffluent passes through lines 23 and 24 through heater 25 and transfer line 26 to tail reactor 27. Final effluent leaves the tail'reactor through line 28 and passes through exchanger 29 and cooler 30 to hydrogen separator 31 from which separated hydrogen is withdrawn" through line 32, net hydrogen being vented through line 33 and the required amount of recycle hydrogen being recycled by compressor 34 to line 13.

The pressure in the reactors is maintained at about" 100 p. s. i. g., i. e. in'the range of about 50 to p; s. i. g., the lead reactor being at somewhat higher and the 'tail reactor at somewhat lower pressure than the intermediate reactor to provide for pressure drop through the ,sys-" tem. Theinlet temperature to each of the reactors'is';

about 930 'F., e. g. in the rangeofabout'900 to 950" but not higher than 975 F." Each of the reactors "is preferably aluminized and provided with a refractory' lining of low iron content. They may each contain about v the same amount of catalyst although, if desired, the subsequent reactors may contain somewhat more catalyst than the lead reactor. The catalyst may be of any known type'of supported platinum catalyst and 'the'plati nurn is'preferably supported on'alumina; it may be prepared by compositing a platinum chloride with an "alu mina support as described, forexample, in U. $2,659,701 and it preferably contains about .3 to- .6 weight percent" of platinum. The space velocity in each reactor is preferably in the range of about 1 to 10, the over-allspace velocity preferably beingin the range of about-l :to- 4 1 volumes I of liquid hydrocarbon charge. "per". hour .per: volume of catalyst.

The product is withdrawn from separator 31 through line 35 to stabilizer and/ or fractionation system diagramma tically represented as fractionating column 36 from which propane and lighter materials are withdrawn through line 37 and stabilized product is withdrawn to benzene recovery system 38 which may be of any known type such as silica gel absorption, extractive distillation or polyethylene glycol extraction (Udex), the benzene being withdrawn from the system through line 39 and products separated from benzene being withdrawn through line 39' for blending with reformed motor fuel.

A swing reactor 40 (containing the same amount of the same type of catalyst as reactor 27) is employed in this example with an inlet line 41 selectively connected to transfer lines 16a, 21a and 26a and with an outlet line 42 with selective connections 18a, 23a and 28a. Thus by proper valve manipulation, the swing reactor may take the place of any on-stream reactor so that the latter may be regenerated.

For effecting regeneration and/ or rejuvenation a purge and regeneration system 43 may be employed with an upper manifold line 44 which may be selectively connected to individual reactors by lines 45, 45a, 45b and 450. The bottom of each reactor may be selectively connected by lines 46, 46a, 46b or 460 to manifold line 47 connected to the other side of the purge and regeneration system. Thus, when catalyst in any reactor requires regeneration, it may be blocked out of on-stream position, purged with hydrogen, regenerated by burning carbonaceous deposits with oxygen diluted by flue gas, rejuvenated by contact with a gas having an oxygen partial pressure of at least .4 and preferably 1 or more atmospheres at a temperature of about 950 to 1050 F. fora period of about .5 to 5 hours or more, purged with flue gas and then purged with hydrogen. The regeneration and rejuvenation technique is described in greater detail in co-pending application Serial No. 416,072, filed March 15, 1954. Water is preferably removed from flue gas introduced and produced in the system during regeneration and such water is removed from the system through line 48. Gases may be purged from the system through line 49.

The methylcyclopentane hydroforming system thus far described is admirably suited for the conversion of methylcyclopentane or virgin naphtha fractions containing 5 to 50 percent or more of methylcyclopentane in order to obtain maximum benzene production with minimum hydrocracking. If desired, any unconverted methylcyclopentane may be separated from the product and recycled. Where cyclohexane is the desired product, the benzene thus produced may be hydrogenated in a separate system with net hydrogen from line 33 with catalysts and under conditions well known for that purpose.

Since production of maximum yields of 95-100 octane number motor fuels from petroleum naphthas is usually the desired objective of a refiner, the methylcyclopentane hydroforming system hereinabove described is preferably integrated with the type of naphtha hydroforming system now known to those skilled in the art, such as Platforming or, preferably, with an Ultraforming system. In such an integrated system a total naphtha charge (which may have been previously hydro-fined) from line 50 is introduced into fractionator 51 from which components boiling below about 140 F. are taken overhead through line 52 and products higher boiling than about 400 to 425 F. are withdrawn as bottoms through line 53. The methylcyclopentane fraction boiling in the range of about 140 to 200 F. or preferably 140 to 180 F. is removed as a side stream and introduced by line 11 to the low pressure hydroforming operation hereinabove described, said charge preferably being substantially free from water, i. e. containing less than about 40 parts per million and usually not more than about parts per million of water. The naphtha fraction boiling in the range of about 180 to about 400 F. or, if desired, about 200 to 360 F. is withdrawn as a side stream through line 54, admixed with about 5 mols of recycled hydrogen from line 55, preheated in coil 56 and introduced by transfer line 57 to lead reactor 58. Effluent from the lead reactor is passed by line 59 through reheater 60 and transfer line 61 to intermediate reactor 62. Effluent from reactor 62 is passed by line 63 through reheater' 64 and transfer line 65 to tail reactor 66. Effluent from the tail reactor.

passes through line 67, heat exchanger 68 and cooler 69 to hydrogen separator 70 from which separated hydrogen is removed by line 71. The net hydrogen produced may be introduced by line 72 through a pressure reducing valve 72a to line 13 for use in the low pressure portion of the system. The amount of hydrogen required for recycle is returned by circulating compressor 73 and line 55 to preheater 56. j

The separated liquid is introduced from separator 70 through line 74 to product recovery system diagrammatically represented by fractionating column 75, the propane and lighter gases being vented from the top thereof through line 76. The light fraction of the reformed product boiling below about 180 to 200 F. is usually of much lower octane number than the heavier portions of the product and may be withdrawn as a side stream through line 77 and introduced to line 14 for hydroforming in the low pressure system wherein it may be further dehydroaromatized. If desired, an intermediate product fraction boiling in the range of about 180 to 250 F. may be recycled by line 78 and pump 79 to line 54. The heavier, highest octane number components of the hydroformed product are withdrawn through line 80 and blended in line 39 with theproducts from the low pressure hydroforming system to give the final gasoline product of 95+ octane number in maximum ylelds.

Reactors 58, 62 and 66 may contain the same type of catalyst as described for use in reactors 17, 22, 27 and 40 and, like those reactors, are preferably alumimzed. However, reactors 58, 62 and 66 are operated at a pressure in the range of 200 to 500 p. s. i. g. or more, preferably in the range of 200 to 350 p. s. i. g., the lead reactor usually being somewhat above 300 p. s. i. g. and' the remaining downstream reactors being at lower pres sures because of pressure drop in the system. The inlet temperature to lead reactor 58 may be in the range of about 850 to 950 F., e. g. about 900 F., and the inlet temperature to the remaining reactors is preferably in the range of about 900 to 975, e. g. about 940 F.-

The space velocity in this system may be substantially the same as in the low pressure system. I

As in the case of the low pressure system, a swing reactor 83 may be employed, this reactor containing about the same amount of the same type of catalyst as in tail reactor 66. The inlet line 84 to the swing reactor may be selectively connected to transfer lines 57a, 61a and 65a. The outlet line 85 may discharge efiluent from the swing reactor through lines 59a, 63a or 67a. Thus the swing reactor may take the place of any on-stream reactor to facilitate regeneration thereof and it may be operated in parallel with any of the on-stream reactors during periods when no regeneration is required.

The same regeneration system hereinabove described in connection with the low pressure system may be utilized for effecting catalyst regeneration and rejuvenation in the higher pressure system, upper regeneration manifold 86 being selectively connected to the reactors by lines 87, 87a, 87b and 870 and the reactors being connected by lines 88, 88a, 88b and 880 to lower regeneration manifold line 89. It will thus be observed that the low pressure methylcyclopentane hydroforming unit is integrated with the higher pressure naphtha hydroforming unit by the use of a common fractionator 51, a com mon regeneration system, by recycle operation which up grades the octane number of low boiling hydroformed naphtha and by the utilization in the low pressure reforming of hydrogen produced in the high pressure reforming.

.While aparticular .e-Xample ofour invention has been described in considerabledetail, it willlbe understood that other examples and alternative arrangements and conditions will be apparent from the above description to those skilled in .the .art. .More than. one intermediate reactor with its corresponding reheater maybe employed in the low 'pressuresystem, the high pressure system, or both.v Instead of employing the swing reactor system, other arrangements .may be provided for blocking out on-stream reactors in order -to provide for regeneration and rejuvenation.

We claim:

1. The method of converting methylcyclopentane in a naphtha charging stock, which method comprises fractionating said naphthato obtain a light naphtha boiling within the range of 140 to 200 F. and containing at least about percentof methylcyclopentane, hydroforming said light naphtha with a supported platinum-catalyst at a pressure above about SO-but below 150 p. s. i. and at a temperature in the range of about 900- to 950 F. in-the presenceof about 1 to .10 mols of hydrogen per mol of charge and. also in the presence of about 100 to 500 parts per million of sulfur based on hydrocarbon charge whereby the presence of the sulfur increases benzene production anddecreaseshydrocracking without substantialadverse effecton catalyst activity and selectivity.

2.v The m'ethodofclaim 1 wherein the light naphtha charge is chiefly .methylcyclopentane.

3.- The method of claim 1 wherein the light naphtha charge is a naphtha fraction boiling in the range of about 140 to 180 F.

4. The method of claim 1 .wherein the light naphtha charge is a naphtha fraction boiling chiefly inthe. range of -140 to-'l80 F. in admixture with light hydroformed naphtha product boiling-below 200 F.

5. The method of claim 1 which includes the step of adding sulfur to the light naphtha charge inanvamount in therang of about 50 to 400 parts per million.

. 6. The method of claim 1 whereinlhe hydroforming is efiectedin the presenceof approximately 200 partsper million of sulfur based on methylclcyopentanecharge.

7. The method of obtaining both benzeneand large yields of 95+ octane numbermotor fuel from naphtha hydrocarbons, which method comprises. fractionati g naphtha hydrocarbons to obtain. a 1methylcyclopentane fraction boiling chiefly in the range of about 140 to 180 F. and a heavier naphtha fraction boiling chiefly in the range'ofabout 180 to-T400 F.',-hydroforming the. heavier naphthafraction with a supported platinum catalyst at a hydroforming temperature and at a pressure in the range ofabout 200 to 750 p. s. i., hydroforming the methylcyclopentane fraction with. supported platinum catalyst .at hydroforming temperatures under a pressure above. aboutlSO but below 150 p. s. i. and in the presence of about 100 to 500 parts per million of sulfur based onthe hydrocarbon charge, separating benzene from stabilized products'of the'last named hydroformingstep, and combining therest of the stabilized products with products of the first named hydroforming step to obtain said octane number motor fuel.

8.'The method of claim 7 wherein at least the methylcyclopentane hydroforming step is 'efiectedin a regenerativesystem and wherein hydrogen produced in' the heavier naphtha hydroforming step is supplied to the methylcyclopentane hydroforming step.

9. The method of claim 7 wherein both hydroforming steps are effected in regenerative systemsandwhich. includes. the steps of introducing regeneration gases to both hydroforming steps "from a common regeneration system.

10. The method 'of claim 7 which includes the step of obtaining from heavier hydroformed naphtha product a fraction boiling below about 200? F. and introducing said'last named fraction together with the methylcyclopentane fraction to' the hydroformingoperation which is effected at the pressure above 50 and below 150 p., s. i.

11. The method. of minimizing hydrocracking and maximizing benzene production in the hydroforming over supported platinum catalystof a naphtha fraction boiling in'the range ofabout 140 to 200 F. and containing a substantial amount ofmethylcyclopentane, which method comprises hydroforming .said fraction at a pressure of about p. s. i. in the presence of about 200 parts per million of sulfur.

. 12. The methodof claim 11 wherein the naphtha fraction boiling in the range of '140 to 200 F. consists chiefly of methylcyclopentane.

\ References Cited in the file ofthis patent UNITED STATES PATENTS 2,604,438 Bannerot July 22, 1952 2,636,909 Oblad et a1 Apr. 28, .1953 2,653,175 Davis Sept. 22, 1953 

1. THE METHOD OF CONVERTING METHYLCYCLOPENTANE IN A NAPHTHA CHARGING STOCK, WHICH METHOD COMPRISES FRACTIONATING SAID NAPHTHA TO OBTAIN A LIGHT NAPHTHA BOILING WITHIN THE RANGE OF 140 TO 200*F. AND CONTAINING AT LEAST ABOUT 5 PERCENT OF METHYLCYCLOPENTANE, HYDROFORMING SAID LIGHT NAPHTHA WITH A SUPPORTED PLATINUM CATALYST AT A PRESSURE ABOVE ABOUT 50 BUT BELOW 150 P.S.I. AND AT A TEMPERATURE IN THE RANGE OF ABOUT 900 TO 950*F. IN THE PRESENCE OF ABOUT 1 TO 10 MOLS OF HYDROGEN PER MOL OF CHARGE AND ALSO IN THE PRESENCE OF ABOT 100 TO 500 PARTS PER MILLION OF SULFUR BASED ON HYDROCARBON CHARGE WHEREBY THE PRESENCE OF THE SULFUR INCREASES BENZENE PRODUCTION AND DECREASES HYDROCRACKING WITHOUT SUBSTANTIAL ADVERSE EFFECT ON CATALYST ACTIVITY AND SELECTIVITY. 